Valve Model Research Articles

Ahmed glaucoma valve implant for refractory glaucoma in children: A systematic review and meta-analysis.

The aim of this study was to evaluate the efficacy and safety of the Ahmed glaucoma valve in pediatric patients with refractory glaucoma. A comprehensive literature search was conducted across multiple major databases, including PubMed, Embase, the Cochrane Library of Systematic Reviews, Science Direct, China's National Knowledge Infrastructure, and the Wanfang database. We retrieved studies published before December 2022 that met the inclusion criteria, including clinical controlled trials (randomized controlled trials) and clinical noncontrolled trials (non-randomized controlled trials) on the use of Ahmed glaucoma valve in pediatric patients with refractory glaucoma. We performed a meta-analysis and systematic review. The efficacy measures included intraocular pressure, number of anti-glaucoma medications, visual acuity, and success rate. The safety measures were complications. Statistical analysis was performed using RevMan 5.0 software. We identified 46 eligible studies: Compared with geographic location and study type, the Ahmed glaucoma valve showed a decrease in postoperative intraocular pressure and number of anti-glaucoma medications compared to preoperative levels in children with refractory glaucoma (P < 0.001). Compared with etiological, the Ahmed glaucoma valve showed a decrease in intraocular pressure after surgery compared to preoperative levels in children with refractory glaucoma (SMD: 14.57, 95% CI: 14.05-15.08, P < 0.00 1), and a decrease in postoperative number of anti-glaucoma medications compared to preoperative number of anti-glaucoma medications (SMD: 1.45, 95% CI: 1.37-1.54, P < 0.001). Compared with trabeculectomy revision surgery, there was no significant difference in the complete success rate between the two groups (SMD: 0.86, 95% CI: 0.52-1.39; P = 0.37).Overall, the postoperative intraocular pressure at the time of Ahmed glaucoma valve implantation was lower than that at the time of trabeculectomy revision surgery (SMD: 1.01, 95% CI: 0.71-1.31, I2 = 99%, P < 0.001). Subgroup analyses based on whether mitomycin C was use d or not. There was a statistically significant difference in intraocular pressure between Ahmed's glaucoma valve surgery and preoperative (SMD: 14.13, 95% CI: 13.47-14.80, P = 0.007). Comparison of cumulative complete success rates of Ahmed S2, S3, and Ahmed FP7, FP8 in Ahmed glaucoma valve surgery (SMD: 0.74, 95% CI: 0.38-1.45, I2 = 85%, P = 0.38). There is no statistical difference between the two groups. Choroidal effusion and anterior chamber hemorrhage are the two most common adverse events after Ahmed's glaucoma valve surgery. The Ahmed glaucoma valve implantation has some effectiveness in reducing intraocular pressure in children with refractory glaucoma, but there are still many complications. Valve model may not be the key factor affecting the postoperative effectiveness and adverse reactions of refractory glaucoma in children.

3-D Numerical Study of Cavitation Evolution Through A Butterfly Valve Model at Different Regulating Conditions

3-D Numerical Study of Cavitation Evolution Through A Butterfly Valve Model at Different Regulating Conditions

Unraveling the molecular complexity of bicuspid aortopathy: Lessons from comparative proteomics.

Molecular markers and pathways involved in the etiology and pathophysiology of bicuspid aortopathy are poorly understood. The aim here is to delve into the molecular and cellular mechanisms of the disease and identify potential predictive molecular markers using a well-established isogenic hamster model (T-strain) of bicuspid aortic valve (BAV) and thoracic aortic dilatation (TAD). We carried out comparative quantitative proteomics combined with western blot and morpho-molecular analyses in the ascending aorta of tricuspid aortic valve (TAV) and BAV animals from the T-strain, and TAV animals from a control strain. This strategy allows discriminating between genetic and hemodynamic factors in genetically homogeneous populations. The major molecular alteration in the aorta of genetically homogeneous BAV individuals is PI3K/AKT overactivation caused by changes in the EGF, ANGII and TGF-β pathways. PI3K/AKT affects downstream eNOS, MAP2K1/2, NF-κB, mTOR and WNT pathways. Most of these alterations are seen in independent patient studies with different clinical presentations, but not in TAV hamsters from T-strain that mainly exhibit WNT pathway downregulation. Therefore, we identify a combination of defective interconnected molecular pathways, directly linked to the central PI3K/AKT pathway, common to both BAV-associated TAD patients and hamsters. The defects indicate smooth muscle cell shift towards the synthetic phenotype induced by endothelial-to-mesenchymal transition, oxidative stress and inflammation. WNT signaling represent one genetic factor that may cause structural aortic abnormalities and aneurysm predisposition, whereas hemodynamics is the main trigger of molecular alterations, probably determining aortopathy progression. We identify twenty-seven novel potential biomarkers with a high predictive value.

Deep-Learning-based Automated Identification of Ventriculoperitoneal-Shunt Valve Models from Skull X-rays.

Ventriculoperitoneal shunts (VPS) are an essential part of the treatment of hydrocephalus, with numerous valve models available with different ways of indicating pressure levels. The model types often need to be identified on X‑rays to assess pressure levels using amatching template. Artificial intelligence (AI), in particular deep learning, is ideally suited to automate repetitive tasks such as identifying different VPS valve models. The aim of this work was to investigate whether AI, in particular deep learning, allows the identification of VPS models in cranial X‑rays. 959 cranial X‑rays of patients with aVPS were included and reviewed for image quality and complete visualization of VPS valves. The images included four VPS model types: Codman Hakim (n = 774, 81%), Codman Certas Plus (n = 117, 12%), Sophysa Sophy Mini SM8 (n = 35, 4%) and proGAV 2.0 (n = 33, 3%). AConvolutional Neural Network (CNN) was trained using stratified five-fold cross-validation to classify the four VPS model types in the dataset. Afinetuned CNN pretrained on the ImageNet dataset as well as amodel trained from scratch were compared. The averaged performance and uncertainty metrics were evaluated across the cross-validation splits. The fine-tuned model identified VPS valve models with amean accuracy of 0.98 ± 0.01, macro-averaged F1 score of 0.93 ± 0.04, arecall of 0.94 ± 0.03 and aprecision of 0.95 ± 0.08 across the five cross-validation splits. Automatic classification of VPS valve models in skull X‑rays, using fully automatable preprocessing steps and aCNN, is feasible. This is an encouraging finding to further explore the possibility of automating VPS valve model identification and pressure level reading in skull X‑rays.

Numerical Analysis of the Influence of Frost Layers on the Heat Transfer Characteristics of Cryogenic Valves for Polar LNG Ships

To investigate the impact of frost-layer formation on the heat transfer characteristics of cryogenic valves in LNG vessels, this study derived the temporal variation in the valve’s temperature field based on the thermodynamic characteristic parameters of the low-temperature valve. Additionally, a frost formation model was developed for the drip tray. This considered the physical model characteristics of the tray, and the frost thickness was calculated for different times. The morphology of the calculated frost layer was coupled with the low-temperature valve model for heat transfer calculations to explore the influence of the frost layer on valve heat transfer characteristics. The results show that, in the initial stage of frost formation, the frost layer acts similarly to a finned heat sink, enhancing the thermal exchange efficiency at the surface of the drip tray, which results in a temperature increase in the drip tray and stuffing box compared to the frost-free condition. However, as the frost layer grows on the surface of the drip tray, the surface heat transfer resistance increases, gradually diminishing the enhancing effect of the frost layer on the heat dissipation of the drip tray. The results validate the dual role of the frost layer in the heat transfer process of low-temperature valves, providing important insights for the design and optimization of such valves.

Anodic Cold Start Control of PEM Fuel Cell System with Temperature Dependent Solenoid Valve Model

Anodic Cold Start Control of PEM Fuel Cell System with Temperature Dependent Solenoid Valve Model

Validation and Refinement of Fluid Dynamics Models for Vacuum Pressure Relief Valves Based on Data Analysis

Validation and Refinement of Fluid Dynamics Models for Vacuum Pressure Relief Valves Based on Data Analysis

Contemporary Management of the Aortic Valve-Narrative Review of an Evolving Landscape.

Background: Aortic valve replacement has undergone novel changes in recent decades, providing not only a multitude of procedural options but expanding the treatable patient population. Specifically, a number of minimally invasive and interventional treatment options have allowed for the treatment of high and prohibitive risk surgical patients. Further, technology is allowing for the development of innovative surgical and transcatheter valve models, which will advance the treatment of aortic valve disease in the future. Objective: Here, we choose to describe the modern aortic valve replacement techniques and the available valves and designs.

Algorithmic Generation of Parameterized Geometric Models of the Aortic Valve and Left Ventricle

Simulating the cardiac valves is one of the most complex tasks in cardiovascular modeling. As fluid–structure interaction simulations are highly computationally demanding, machine-learning techniques can be considered a good alternative. Nevertheless, it is necessary to design many aortic valve geometries to generate a training set. A method for the design of a synthetic database of geometric models is presented in this study. We suggest using synthetic geometries that enable the development of several aortic valve and left ventricular models in a range of sizes and shapes. In particular, we developed 22 variations of left ventricular geometries, including one original model, seven models with varying wall thicknesses, seven models with varying heights, and seven models with varying shapes. To guarantee anatomical accuracy and physiologically acceptable fluid volumes, these models were verified using actual patient data. Numerical simulations of left ventricle contraction and aortic valve leaflet opening/closing were performed to evaluate the electro-physiological potential distribution in the left ventricle and wall shear stress distribution in aortic valve leaflets. The proposed synthetic database aims to increase the predictive power of machine-learning models in cardiovascular research and, eventually, improve patient outcomes after aortic valve surgery.

Design, experiment and modeling of a damper based on magnetic gradient pinch mode MR valve

Abstract In this study, a novel Magnetorheological (MR) damper designed based on the Magnetic Gradient Pitch Mode MR (MGPMR) valve, is investigated analytically and experimentally. The prototype and experimental platform are designed and established to characterize the dynamic force- displacement/velocity properties under board ranges of excitation and current conditions with the consideration of the effect of design parameters, which mainly includes the number of the non-magnetic rings and the diameter of the flow channel. The experimental data shows that the tunable damping range is positive correlation with the number of non-magnetic rings and negative correlation with the diameter of flow channel. Therefore, an analytical model, which considers the hysteresis damping model of the MGPMR valve, ideal gas model, and the hysteresis friction of seals, is established to describes the dynamic force- displacement/velocity properties of the MGPMR damper with 4 non-magnetic rings and 7mm diameter of the MGPMR valve. The proposed hysteresis damping model of the MGPMR valve consists of the tangential hyperbolic hysteresis model, tunable viscous damping, and fluid inertial together with the identified model parameters. The validity of the proposed model of MGPMR damper is demonstrated through a comparison between the simulation and experiment results showing good agreement of the hysteresis loops and output force-displacement/velocity characteristics under wide range of excitation and currents conditions.&amp;#xD;

Model of reed valve dynamics in unsteady flow, solution algorithm, and validation on a single-cycle rig

The results of studying an application model of unsteady flow through the reed valve assembly of a two-stroke piston engine are presented. The main goal was to develop and validate a model based on the check valve calculation scheme in the ALLBEA software package. The principles of modeling the valve motion dynamics in conjunction with a one-dimensional model of gas dynamics, as well as the algorithmic presentation of calculations for their implementation in the package, are briefly discussed. An approach to valve model identification and the proposed method for adjusting the model coefficients are considered. For the identification and validation of the model the data obtained from a single-cycle experimental setup were used, in which flow through the reed valve with finite amplitude waves in the pipeline was organized. The conducted research contributes to the analysis and optimization of processes in pipelines, pumps, and engines, promotes the development of applied models, software tools, and calculation methods in the specified areas.

Multi-objective optimization of an electrical injector in Urea-SCR system

Electrical injector is mainly used in non-air-assisted urea dosing systems to atomize and inject urea water solution. It consists of solenoid switch valve and injector. A good performance of the electrical injector can improve dosing precision of urea dosing system. To investigate dynamic characteristics of the electrical injector, an equivalent magnetic circuit model of the solenoid valve was established and magnetic field of the solenoid valve was also simulated using a three-dimensional finite element model. The results show that the calculation error of the two models is 6%, demonstrating that the equivalent magnetic circuit model can effectively predict the magnetic characteristics of the solenoid. Taking opening time, closing time, and coil area of the electrical injector as objective functions, a multi-objective optimization algorithm was used to optimize the design parameters of the electrical injector. Opening and closing processes of the optimized electrical injector under different pressures and driving voltages were measured through laser triangulation sensor. The experimental results showed that calculation results of the proposed theoretical model were close to the measurement results. The opening time of the optimized injector has been reduced by 11%, the response of the injector has significantly improved.

Simulation and experiment of static and dynamic characteristics of pilot-operated proportional pressure reducing valve

As an important control component in hydraulic system, the static and dynamic performance of electro-hydraulic proportional valve directly affects the performance of the whole control system. In this paper, through the analysis of the operating principle of a specific pilot-operated proportional reducing valve, two static and dynamic mathematical models are established to simulate the performance of the valve. One model is constructed by empirical formulas, while the other one is corrected through CFD simulation and proportional solenoid test, firstly, a series of flow and fluid force interpolation models are obtained through CFD simulation, replacing the original empirical formulas. Secondly, relevant parameters of the proportional solenoid are corrected by testing its static and dynamic characteristics. To validate the validity of model correction and the accuracy of the corrected model, the static and dynamic experiments of the valve were conducted, and the results are compared with the simulation results of the models, which show that the experimental results are in better agreement with the simulation results of the corrected model. Therefore, this model can be used for further research on the valve.

Utilizing a Transparent Model of a Semi-Direct Acting Water Solenoid Valve to Visualize Diaphragm Displacement and Apply Resulting Data for CFD Analysis

This article introduces a comprehensive methodology that combines physical prototyping and computational modeling to analyze the hydrodynamics and design of a semi-direct acting solenoid valve for water applications. A transparent, injection-molded valve model was used to experimentally measure diaphragm displacement, which exhibited linear behavior at flow rates up to 10.1 L/min. Beyond this threshold, the diaphragm reached maximum displacement, constraining flow control accuracy. These experimental results informed the creation of a computational domain for detailed CFD analysis, demonstrating strong validation against experimental pressure drop data. The CFD simulations identified critical inefficiencies, such as uneven pressure distribution on the diaphragm due to inlet flow, flow imbalances, and vortex formation within the chamber and outlet channel. These issues were traced to specific design limitations. To address these design flaws, this study suggests optimizing the inlet geometry, implementing a symmetric chamber design, and modifying the outlet channel with smoother transitions to enhance flow control and improve operational efficiency.

Study on pH control of marine acid injection mixture based on linear active disturbance rejection

Abstract In pH control system of acid injection mixture, the flow rate is easily disturbed due to the constant change of displacement in the platform acid flow control loop and the platform water flow control loop. In this study, a control strategy is proposed, that is, both the inner and outer ring controllers are linear active disturbance rejection controllers. The controller adopts linear active disturbance rejection controller, and the pH value of the mixture is controlled by cascade ratio. On the basis of the second order controller, the second order linear active disturbance rejection controller is designed based on the electric throttle valve and mixing tank model, and the simulation platform of pH control system of acid injection mixture is built by MATLAB(MATrix LABoratory)/Simulink. The controller design and simulation results of linear active disturbance rejection control algorithm and PID(Proportional Integral Derivative) algorithm are compared respectively. The simulation results show that under the interference of external uncertainties, the designed controller can not only track pH value quickly, but also reduce the overshoot and the stability time when disturbed, and effectively improve the dynamic response performance and robustness of the system.

Static and Thermal Analysis of Internal Combustion Engine Valves

Abstract: In this paper the 3D model of the internal combustion engine valves was realized using Autodesk Inventor Professional 2024 and finite element analysis, static and thermal was performed, in order to determine the state of stress, deformation and temperature evolution, by applying restrictions and loads conditions. Two materials were chosen, for internal combustion engine valves, in accordance with the specialized literature. The materials taken for static and thermal analysis was Stainless Steel AISI 446 and NiCr0TiAl. Following the comparative study for the two models, it can be specified the importance of the material for the construction of the internal combustion engine valves who depends on the material properties and their design.

The comparison of echocardiographic and serum parameters between Sapien 3 Ultra Resilia and Sapien 3 at one month

Abstract Background Sapien 3 Ultra Resilia (S3UR) is the latest balloon-expandable valve for transcatheter aortic valve replacement (TAVR). Compared to Sapien 3 (S3), previous model of balloon-expandable valve, the leaflets are modified to anti-calcification tissue and the outer skirt becomes 40% higher with textured polyethylene terephthalate. However, it is unknown how these structural changes affect echocardiographic and serum parameters after TAVR. Purpose To compare impacts of these design changes on relevant echocardiographic and serum parameters between S3UR and S3 in the short term. Methods Patients with severe aortic valve stenosis who underwent TAVR with S3 or S3UR were included in this study. Echocardiographic parameters and blood samples were retrospectively collected at discharge and at 1 month post-procedure. Echocardiographic outcomes included mean pressure gradient (PG), effective orifice area index (EOAi), and paravalvular leak (PVL) grade. Hemolytic anemia indicators, specifically lactate dehydrogenase (LDH) and hemoglobin (Hb), were also assessed. Findings suggestive of hemolytic anemia at 1 month were defined as "an increase in LDH level of ≧200 IU/L as well as a decrease in Hb level of ≧1.0 g/dL from pre-procedure." Results Among 443 patients (S3: April 2020-March 2023, S3UR: April 2023-December 2023), 339 patients (S3: n=270, S3UR: n=69) were available for this study. The mean PG was significantly lower in the S3UR group compared to the S3 group at discharge and at 1 month (Figure 1A). On the other hand, the EOAi was similar between the two groups at discharge and at 1 month (Figure 1B). Although the prevalence of none/trace PVL was significantly higher in the S3UR group at discharge, this difference disappeared at 1 month (Figure 1C). LDH levels were significantly increased from pre-procedure to 1 month in both groups (Figure 2A). The median of ΔLDH (1 month – pre-procedure) and %change of LDH (ΔLDH/ pre-procedure) were significantly higher in the S3UR group. The prevalence of hemolytic anemia at 1 month was also significantly higher in this group (Figure 2B). Conclusion At 1 month, S3UR demonstrated superiority in mean PG but equivalence in EOAi and PVL grade compared with S3. Although both S3UR and S3 showed significant increase in LDH from pre-procedure to 1 month, hemolytic anemia was experienced more frequently in S3UR cases. Further evaluation will be needed to assess the potential clinical impacts of these differences.

Simulation analysis and experimental research on static performance of water-hydraulic pressure difference control valve

Many hydraulic tools, like hydraulic cylinders and hydraulic artificial muscle joints are operated by adjusting pressure differences between different zones. Typically, the method employed to change the pressure difference is establishing hydraulic bridges and adjusting liquid resistance. While effective, this method's drawback is complex structures. To address this issue, a water-hydraulic pressure difference control valve, integrating two hydraulic bridges, was designed. The static performances including the output pressure difference, the flow rate and the force acting on the valve core were analyzed using AMESim and computational fluid dynamics simulations. Based on the simulation results, a prototype of voice coil motor direct drive pressure difference control valve was manufactured and the corresponding experiments were carried out. The computational fluid dynamics simulation results show that the internal leakage and the through-flow capacity difference between throttling grooves affect the flow field characteristics of the valve. When the pump pressure is 3 MPa and the valve opening is at the middle position, the internal leakage increases the flow rate from 2.25 L/min to 2.38 L/min, and the through-flow capacity difference reduces the control port pressure from the theoretical analysis of 1.5 MPa–1.41 MPa. Furthermore, combined with the analysis of the external liquid resistance, the AMESim model of the pressure difference control valve is modified. When the pump pressure is 3 MPa, the pressure difference and flow rate average deviations between the modified AMESim model and the experiment are 0.021 MPa and 0.048 L/min. Finally, a rotational angle experiment for a water hydraulic artificial muscle joints showed satisfactory control effects, suggesting the valve's application in controlling hydraulic tools and actuators.

Numerical analysis of fluid-thermal-structure coupling characteristics of CO2 booster pump valve

CO2 booster pump valves are key components in the CO2 oil drive industry, and their reliability is critical to the safe operation of pumping booster systems. Due to the special nature of CO2, heat transfer occurs during valve movement, which can cause damage to the valve body and poppet, and thus in-depth studies on CO2 properties are needed to better predict the locations where the valve is vulnerable to damage. However, relatively few studies have been conducted to analyze the fluid-thermal-solid coupling failure of CO2 booster pump valves. This paper establishes a multi-physics coupled thermodynamic model of CO2 booster pump valves, analyzes the transient simulation of valves at different valve openings, pressures and temperatures, and investigates the thermal properties of four different poppet materials. The results show that: with the increase of valve opening, the maximum deformation of the valve decreases sharply, and then tends to stabilize; in the process of pressure increasing from 4.77 MPa to 10.52 MPa, the turbulent kinetic energy inside the valve increases by about 78 %; it is also found that the thermal deformation of different poppet materials is directly proportional to the coefficients of thermal expansion of the materials, among which the deformation of aluminum alloy poppet is the largest. In addition, the results of thermal deformation and thermal stress distribution indicate that the failure region of the valve is usually concentrated in the poppet and its corresponding body wall. These results provide theoretical references for optimizing the structural design of CO2 booster pump valves and help reduce the risk of failure of CO2 booster pump valves.

Dynamics and experimental study of a novel proportional directional valve with displacement feedback groove controlled by high-speed switching valves

The intelligence of hydraulic roof support is an important guarantee for unmanned fully mechanized coal mining face. The water-based medium proportional directional valve is the main factor that restricts the intelligent realization of support system. The support control valve needs to meet the 2/3 (two-position three-way) structure, taking into account both manual and electro-hydraulic control functions. The current water-based proportional valve does not satisfy the structural or functional demands of the support system. In this paper, a novel 2/3 water-based proportional directional valve is presented based on the displacement-flow feedback principle, which has two control modes: manual on-off control and electro-hydraulic proportional control. The proportional valve comprises two main valve spools and two pilot valves. The pilot valve is composed of a 2/3 on-off valve with manual operation capability and a high-speed switching valve group controlled by PWM (Pulse Width Modulation). The mathematical model of the proportional valve is established, and the experimental system is built to verify the characteristics of proportional valve. The proportional valve can meet the special functional requirements of the support. In the proportional control mode, the adjustment of spool displacement is regulated through the modulation of PWM duty ratio, resulting in effective control performance of the proportional valve. Furthermore, the discontinuous flow of the high-speed switching valve causes the pressure fluctuation of the pilot hydraulic bridge. Increasing the carrier frequency of PWM can reduce the amplitude of control chamber pressure and spool displacement fluctuation. The findings of the study can offer valuable insights for the continued advancement and enhancement of water-based proportional valves used in hydraulic roof support systems.